GPS Map. I am a green dot in the center. Cops are a blue & red flashing dot. I can't wait!

07-07-2005, 07:40 PM

dmurray14

Quote:

Originally Posted by spence3030

hello there, yes while i am new to the forums, i do read them all the time.
i right now am in the process of plannning out carputers for me and my roomate.

however, this is the tricky part. we have been asking around, but due to lack of knowledge we are at a dead end.

i have an idea for integrated software for the the GPS systems everyone has.

here we go:

1.all emergency personel have radios.
2.all of these radios transmit frequencies(some passive, which would be best, and some are active)
3.you can triangulate cell phones right? so why cant we triangulate police and emergency radios.
4. my roomate has been talking with friends at several tech. schools in CO, but this is beyond their scope.

point to all of this. if we can find a way to use the radio frequencies of the police officers and the precints, along with other stations they call into( i.e. hospitals, ambulance, etc.) then we can use all of these points along with our cars to then show where they are at anytime on our GPS screens.

any feedback whatsoever would be helpful.

thanks,
spence

You do realize that the "tri" in triangulation stands for 3 right? That means you need 3 antennas, and it's a little hard to be in 3 places at once.

07-07-2005, 08:24 PM

RPM_VR4

Wi-Fi baby! As long as there are 2 other people with Wi-Fi enabled CarPCs near you, you got cop scan. ;)

Really though, it might be possible to mount 3 antennas on one car. Maybe even 4, one at each corner of the car, might provide better coverage.

07-07-2005, 09:19 PM

dmurray14

Quote:

Originally Posted by RPM_VR4

Wi-Fi baby! As long as there are 2 other people with Wi-Fi enabled CarPCs near you, you got cop scan. ;)

Really though, it might be possible to mount 3 antennas on one car. Maybe even 4, one at each corner of the car, might provide better coverage.

are you kidding? Only thing you'd be able to tell with 3 antennas on the same car is whether there is a cop inside it...

07-07-2005, 09:21 PM

RPI Geek

Quote:

Originally Posted by dmurray14

You do realize that the "tri" in triangulation stands for 3 right? That means you need 3 antennas, and it's a little hard to be in 3 places at once.

Theoretically you could just drive your car around and if you weren't driving in a straight line you could just use three measurements to guesstimate the location based from these measurements.
I'd be more worried about scanning for the whole spectrum that the police use and figuring out distance or direction considering the interference from the outside world and everything. There's reflections, dead spots, high vs low ground, high tension power lines, etc.
I wouldn't want to be the one to develop the code

07-07-2005, 09:24 PM

RPI Geek

Quote:

Originally Posted by RPM_VR4

Wi-Fi baby! As long as there are 2 other people with Wi-Fi enabled CarPCs near you, you got cop scan. ;)

And from how far away can you reliably get a signal? Something like WiFi might work but not the cards that mere mortals have in their carPCs (or homes if they're feeling benevolent).

07-07-2005, 10:41 PM

Wiredwrx

Quote:

Originally Posted by dmurray14

are you kidding? Only thing you'd be able to tell with 3 antennas on the same car is whether there is a cop inside it...

Well, that is false.

As long as these is a 1/4 wavelength of more of distance between the antennas, you are fine. you will need sophisticated equipment that can measure the time difference of the recieved signal for the three antennas. How do you think LoJack works. That is why there are 4 antennas on the roof of cop cars for lojac. The lojac receiver measures the time difference of the received signal from the antenna

HOWEVER, with the antennas on the roof, you will only know a direction the officer is in from your location, you will not know what thier location actually is. For that, you must have antennas in at least 3 places around the officer. You will again need very sophisticated timing equipment, and a way to conect them together. Wifi might work, but you will have to have at least 3 locations with antennas, equipment, and an internet connection. Then, the carputer will require a connection (Not all that hard, but a consideration). Also, there will be no way to know which officer is where, and where they have moved to. So, since a police car moves through out the day, you will have dots all over the place. You will never be able to know who has moved where.

well it would be easier to just figure out the DISTANCE to the nearest cop car... at least you'd know if you were getting close to one... and then you should only need one antenna and a whole lot less control circuitry.

07-14-2005, 12:24 PM

grepzen

also.... most 'current' police bands use f'trunking and aren't on a set freq